Abstract

We investigate the decay B+→J/ψϕK+ in a search for the X(4140) state, a narrow threshold resonance in the J/ψϕ system. The data sample corresponds to an integrated luminosity of 10.4 fb−1 of pp¯ collisions at s√=1.96 TeV collected by the D0 experiment at the Fermilab Tevatron collider. We observe a mass peak with a statistical significance of 3.1 standard deviations and measure its invariant mass to be M=4159.0±4.3(stat)±6.6(syst) MeV and its width to be Γ=19.9±12.6(stat)+3.0−8.0(syst) MeV.